1. Field of the Invention
The present invention relates to an adjustable monocular eye shield for telescopes and similar instruments and in particular to optical masking or occluding devices for obstructing the field of view of one eye while the other eye is being used to view an image through an ocular or eyepiece. Often it is preferable to occlude the vision in one eye to prevent stereoscopic vision or binocular rivalry from occurring when viewing an image at the exit pupil of a monocular instrument. The term "monocular" as used herein, refers to optical instruments and similar devices having a single eyepiece or ocular designed for viewing an objective image.
The optical telescope in its rudimentary form was first introduced more than three centuries ago. One unique feature and characteristic of optical telescopes whether of the reflecting or refracting type, are that they employ a monocular or single eyepiece for viewing an image at the exit pupil. Telescopes and similar monocular optical instruments can usually be used with either the left or right eyes to view an objective image without particular encumbrances to the user. A subject of this invention is that when using a telescope this leaves one eye unoccupied or unused in viewing the image being produced or formed at the exit pupil or eyepiece.
One way the telescope user has addressed the problem of binocular vision is by either closing the eyelids surrounding one eye or by covering the eye with their hand when viewing an image through an ocular or eyepiece. This is often done to prevent impinging light from entering the retina of the eye not used to view an image through the eyepiece. Impinging light that is not masked can detract from the image being viewed in the ocular or eyepiece. An annoyance and a consequence often associated with either closing the eyelids of one eye or covering it with a hand during prolonged periods of viewing is muscle fatigue. Muscle fatigue can occur in muscles of the upper chest, back, shoulders, in the arms or the hand used to cover the eye, or in the periocular muscles of one either eye if the eyelids are closed. Additionally the visual impairments created by peripheral ocular muscle fatigue, discomfort and eye strain can often reduce the user's ability to focus an optical instrument accurately.
2. Description of the Related or Prior Art
A thorough description of the prior art in the field of this invention and in the related fields of retractable eye shields and optical occluding devices can be found in U.S. Pat. No. 4,810,078 to Armstrong (March 1989) and U.S. Pat. No. 4,824,235 to Eddy (April 1989). Of the known related or prior art inventions, only this unique and new innovation of an adjustable monocular eye shield includes a substantially enclosed optical mask, a multiple axis positioning mechanism with a cantilever arm and an eyepiece adapter bracket designed to be fitted over an eyepiece's barrel or tube as they are known in the art.
Eyepieces for small telescopes are commonly available in three standard sizes of 0.965, 1.250 and 2.000 inches. Standard size as it is known in the art refers to the outside diameter of the barrel or tube portion of an eyepiece. The barrel or tube is typically an internally threaded hollow cylinder that extends from the lens cell portion of an eyepiece and performs three basic functions. It is used optically to align the eyepiece lens at the exit pupil, its peripheral surface provides a setscrew platen for mechanically securing the eyepiece to an instrument and its internal threads can be used to attach a filter or similar device. The lens cell portion of an eyepiece holds and secures the lens and is generally larger in diameter than the barrel portion. Standardization of barrel or tube sizes within the industry allows eyepieces' to be easily interchanged among telescopes accepting the same nominal size eyepiece and it is a subject of this invention to find advantage in this similarity.
When using a telescope, positioning the eye at the telescope exit pupil or at the eyepiece is generally necessary to properly view or focus an objective image. Having to center the eye on the optical axis while focusing and maintaining proper eye relief has always been a significant limitation to fitting any telescope with a practical eye shield. A practical eye shield must readily adapt to changes in eyepiece focal lengths, be easily adjustable for the users' interpupillary dimension, allow for telescope positioning or orientation about the X, Y and Z axis, adjust to the users' head and eye position, allow for focus mechanism movement and changes in longitudinal position, provide for adequate eyepiece relief and for attachment of other ancillary optical components near the telescopes exit pupil position.
It is the subject of this invention to disclose such an apparatus or device and its mechanisms that are suitable for use with telescopes and similar monocular instruments and to address the deficiencies, inconveniences and quandaries associated with related or prior art appliances.